Milk

Milk, the fluid secreted by the mammary glands of all female mammals for the support of their young. It consists of a solution of sugar, albuminoids, and salts, together with a certain amount of fat. The milk of all mammals is the same in the nature of its constituents, but the proportion in which they are present varies very much.

Milk contains about 80 or 90 per cent. of water, and in that of the cow there is about 5 per cent. cream. When churned the globules (of which milk is largely composed) unite, and butter is formed, the residue being the buttermilk. If rennet (q.v.) be added to skimmed milk, curds and whey will be formed. Cheese is made by allowing the whey to separate and adding salt to the curds. Milk ferments spontaneously, the milk-sugar [Lactose] being converted into lactic acid (q.v.), alcohol, and carbonic acid gas.